Low viscosity cellulose acetate spinning solutions



United States Patent LOW VISCOSITY CELLULOSE ACETATE SPINNING SOLUTIONSJohn D. Brandner, Wilmington, Del., assignor to Atlas Powder Company,Wilmington, Del., a corporation of Delaware No'Drawing. Filed-Nov.27,-1957, Ser. No. 699,192 lllClaims. (Cl. 106-196) The presentinvention relates to low viscosity cellulose acetate spinning solutions.More particularly it pertains to spinning solutions of cellulose acetatein acetone which have a reduced viscosity due to the presence of a smallamount of a salt of an alkyl aryl sulfonic acid.

ing constituent'of the solution, it is desirable to use as high aconcentration of it as possible. However, there is a positivecorrelation between the concentration of the acetate and the viscosityof the solution. As the concentration increases the viscosity increasesuntil, eventually, the solution becomes too viscous for use in anypractical extrusion or fiber forming process.

In the prior art, this problem of high viscosity was solved by adding asmall amount of water to the spinning solution. The addition of thiswater lowers the viscosity to the point where the solution becomesworkable and consequently, water is commonly found in spinning solution.Unfortunately, the use of water retards development of tensile strengthin the fibers which are spun from such solutions. The retardeddevelopment of fiber strength, in turn, prevents stretching andorientation of the fibers. The water is also but slowly removable fromthe fibers.

It is an object of this invention to formulate cellulose acetatespinning solutions which have a relatively low viscosity.

Another object of this invention is the production of low viscosityspinning solutions without sacrificing tensile strength development offibers spun therefrom.

A further object of this invention is the formulation of spinningsolutions containing a viscosity-reducing additive which additive neednot be removed from the spun fibers.

Additional objects of the invention will be apparent to those skilled inthe art from a consideration of the description which follows.

According to the present invention, it has been found that solutions ofcellulose acetate of reduced viscosity are obtained if a smallproportion of a salt of a higher alkyl benzene sulfonic acid is includedin them. These salts may be those formed by alkali metals, ammonia orlower alkyl amines.

Some representative salts which are within the scope of this inventionare as follows: (a) alkali metal saltspotassium dodecyl benzenesulfonate, sodium dodecyl benzene sulfonate (b) ammonia salts-ammoniumdodecyl benzene sulfonate, ammonium decyl benzene sulfonate and (c)amine salts--isopropyl amine dodecyl benzene sulfonate, ethyl aminedodecyl benzene sulfonate, and isopropyl amine dinonyl benzenesulfonate.

2,966,422 Patented Dec. 27, 1960 -'A preferred additive is ethylaminedode'cyl benzene sulfonate.

The additive may be mixed with the cellulose acetate solution in anyconvenient manner either in the solvent for the cellulose acetate or inthe cellulose acetate solution. For ease of mixing, it is oftenexpedient to add the viscosity-reducing agent in solution form. Aromaticpetroleum fractions are useful for this purpose and do not in themselvesappreciably affect solution viscosity.

Any amount of additive which will produce the desired lowering ofviscosity may be used. Usually, amounts below 0.5% by weight of thecellulose acetate are not sufiiciently effective for best results andamounts above 2.0% also seem to produce less desirable results. Amountsbetween these two values are preferable and the most effectiveviscosity-reducing amount usually lies between aboutl and 1.8% of theweight of cellulose acetate.

Whenever the term cellulose acetate is used throughout this disclosureit is intended to means acetone-soluble cellulose acetates, such as thatsold under the name LH-l. These cellulose acetates, which are usuallymarketed in flake form, preferably contain from 57% acetyl radicals and,on a molal basis, have approximately 2.2 mols of acetyl radical per molof glucose radical. The term cellulose acetate is not intended to coveracetates such as cellulose tri-acetate, which contains 62.5% acetylradicals and is not soluble in acetone. This distinction betweencellulose acetate which are suitable for spinning and those which arenot is well recognized in the prior art.

The superiority of compositions of this invention was shown by preparingand testing the following spinning solution formulations:

Example I A spinning solution was prepared using 20 parts by weight of acellulose acetate (LH-l) and 80 parts by weight of acetone.

The initial viscosity of a 200 gram sample of this solution was measuredat 25 C. with a Brookfield Viscometer using the No. 4 spindle at 6r.p.m. The initial viscosity of this control solution was assigned anarbitrary value of 100% and all later determinations of viscosity wererelated to this percentage.

Example 11 To a'portion of the solution of Example I was addedsufficient water to make the weight percent of water (based on thecellulose acetate content) 1.2%. The initial viscosity of this solutionat 25 C. was determined to be 81.7% of that of the solution of ExampleI. This determination is representative of the prior art.

Example III A 50% solution of isopropyl amine dodecyl benzene sulfonatewas prepared using an aromatic hydrocarbon having a specific gravity of0.893 (60/60), a flash point of F., and an initial boiling point of 367F. The solvent is sold under the trademark Solvesso 150.

To a 200 gram sample of the solution of Example I was added sufiicientsulfonate solution to make the sulfonate concentration 1% by weight,based on the cellulose acetate content.

The initial viscosity was measured at 25 C. and found to be 74.7% of theinitial viscosity of the solution of Example I, an improvement of 25.3%.

Example IV A 50% solution of tri-isopropyl amine dodecyl benzenesulfonate in Solvesso 150 was prepared as in Example III. To a 200 gramsample of the solution of Example I was added sufiicient sulfonatesolution to make the sulfonate concentration 1% by weight based on thecellulose acetate content.

The initial viscosity was measured at 25 C. and found to be 57.8% of theinitial viscosity of'the solution of Example I, an improvement of 42.2%.

Example V A 50% solution of ethyl amine dodecyl benzene sulfonate inSolvesso 150 was prepared as in Example III.

To a 200 gram sample of the solution of Example I was added sufficientsulfonate solution to make the sulfonate concentration 1% by weightbased on the cellulose acetate content of the spinning solution.

The initial viscosity was measured at 25 C. and found to be 57.8% of theinitial viscosity of the solution of Example I, an improvement of 42.2%.

Example VI A 50% solution of isopropyl amine dinonyl benzene sulfonatein Solvesso 150 was prepared as in Example III.

To a sample of the solution of Example I was added sufiicient sulfonatesolution to make the sulfonate concentration 1% by weight, based on thecellulose acetate content of the spinning solution.

The initial viscosity was measured at 25 C. and found to be 83.6% of theinitial viscosity of the solution of Example I. After 8 days storage theviscosity of the solution of Example I was 122.5% of its initialviscosity whereas the viscosity of the solution containing isopropylamine dinonyl benzene sulfonate was only 89.8% of the initial viscosityof the solution of Example I.

Example VII The spinning solution of Example V was allowed to age for 8days. Its viscosity, which had initially been 57.8% of the initialviscosity of the control solution (the solution of Example I) onlyincreased to 61.2% of the initial viscosity of the control whereas, ashas been stated above, the 8 day viscosity of the control was 122.5% ofits initial value.

Example VIII The isopropyl amine dodecyl benzene sulfonate solutionprepared as in Example III was added to a sample of the spinningsolution of Example I in an amount to make the sulfonate concentration1.8% by weight, based on the cellulose acetate content.

The initial viscosity was measured at 25 C. and found to be 70% of theinitial viscosity of the solution of Example I.

. The sulfonates may be added to the spinning solution after thecellulose has been dissolved or, alternatively, they may be added to theacetone before dissolving the cellulose. In either case, the effect issubstantially the same.

Spinning solutions containing the additives of the invention are spun inany manner which is conventional for cellulose acetate, such asextrusion through spinnerettes. The fibers thus produced will developtensile strength rapidly and thus be capable of optimum stretching andorientation. In addition, unlike the viscosity reducing additive of theprior art, the instant additives need not be removed from the fiberssince they have no deleterious effect upon them.

Having described my invention, what is claimed is:

1. A spinning solution comprising cellulose acetate, a solvent for saidacetate, and from 0.5 to about 2% by weight, based on the weight of saidcellulose acetate, of a higher alkyl substituted benzene sulfonate, saidsulfonate being selected from the group consisting of alkali metalsulfionates, ammonium sulfonates, and amine sulfonates.

2. The-composition of claim 1 wherein said sulfonates are alkali metalsulfonates.

3. The composition of claim 2 wherein the alkali metal is sodium.

4. The composition of claim 1 wherein said sulfonates are aminesulfonates.

5. The composition of claim 4 wherein the amine is isopropyl amine.

6. The composition of ethyl amine.

7. The composition of claim 4 wherein the amine is tii-isopropyl amine.

8. The composition of claim 1 wherein said sulfonates are ammoniumsulfonates.

9. A spinning solution consisting essentially of cellulose acetate, asolvent for said acetate, and from 0.5 to about 2% by Weight, based onthe weight of said cellulose, of a higher alkyl substituted benzenesulfonate, said sulfonate being selected from the group consisting ofalkali metal sulfonates, ammonium sulfonates and amine sulfonates.

10. The composition of claim 1 wherein said higher alkyl substituent isdodecyl.

claim 4 wherein the amine is References Cited in the file of this patentUNITED STATES PATENTS 1,954,326 Murray et al Apr. 10, 1934 1,957,912Seel May 8, 1934 2,286,822 Malm et al June 16, 1942 Sisley et al.:Encyclopedia of Surface Active Agents 1952 p. 388.

1. A SPINNING SOLUTION COMPRISING CELLULOSE ACETATE, A SOLVENT FOR SAIDACETATE, AND FROM 0.5 TO ABOUT 2% BY WEIGHT, BASED ON THE WEIGHT OF SAIDCELLULOSE ACETATE, OF A HIGHER ALKYL SUBSTITUTED BENZENE SULFONATE, SAIDSULFONATE BEING SELECTED FROM THE GROUP CONSISTING OF ALKALI METALSULFONATES, AMMONIUM SULFONATES, AND AMINE SULFONATES.